1. Field of the Invention
This invention relates to an ink-jet head and its manufacturing method and an ink jet recording device for recording to a record medium to jet a condensed color component in an ink with the color dissipated in a solvent.
2. Description of the Related Art
In recent years, exploitation of an ink-jet printer is implemented actively as one of the information output apparatus, along with improvement of the computer technology and with advance of an information-oriented society. The ink-jet printer records graphs, images and so forth to a record medium such as a recording paper or the like in such a way that a liquid ink is jetted in atmosphere in the semblance of small drops, fine liquid column, or mist. The ink-jet printer generates few noises, since it records with the ink-drops jetted, under the condition of fundamentally non-contact and non-impact record. Further a relatively easy high quality color record by the ink-jet printer can be implemented because it is possible to record to a normal paper without implementation of a complicated processing such as development and fixing and so forth in an electro-photographic printer, and it is possible to superimpose ink-drops of color ink due to a direct record by using the ink.
There are various methods of the ink-jet printer, for example, a bubble jet method in which the bubble is generated instantaneously by the exothermic resistance element, before jetting an ink by pressure of the bubble (K. Hara et. al., Image-Electronics Society Journal, vol.11, 2(1982)), and a method in which the ink is jetted by the pressure pulse generated by using the piezoelectric element or the electrostrictive element with an electrical signal converted to mechanical vibration (E. Stemme et. al., IEEE Trans. ED20-1, p14(1973)). These are representative.
In these ink-jet printers, in all cases an ink nozzle is used. However if the size of the ink nozzle is reduced to enhance the resolution by increasing the number of nozzle, a clogging of the ink nozzle generates easily caused by vaporization of the solvent, which becomes a great cause of lowering of reliability. In the bubble jet method, the bubble due to the vapor in high temperature instantaneously generated is used as the pressure source, there is a problem that solids due to the thermal or chemical reaction in high temperature between the nozzle and the ink, adhere to the wall of the nozzle. In the methods using the piezoelectric element or electrostrictive element, a clogging is generated easily due to the complicated mechanism such as a route of the ink.
In recent years, a printer with higher resolution is required. In the conventional bubble jet method, it is difficult to form an ink-drop whose particle diameter is less than 20 .mu.m. Only minimum dot diameter of about 50 .mu.m is obtained on the record medium. The pressure method by the electrostrictive element becomes very complicated structure, with the result that it is difficult to produce it due to the problem for the processing technology.
As the method to resolve these problems, as shown in FIG. 1, there is a method in which a high voltage is applied between a thin film type electrode and an opposite electrode existing at rear face of a recording paper, drawing an ink-drop from a small slit due to an electrostatic attraction force. As shown in FIG. 2, there is a method in which it is used an ink including a charged color component, the condensed ink is jetted. The former has a slit type nozzle which is not required a nozzle every dot. In the latter, a problem of clogging can be reduced because of a nozzle less method and also a ink-drop can be jetted with fine particle diameter stably generated. An implementation of high resolution is possible.
However, as shown in FIGS. 1 and 2, the head of the ink-jet printer in these electrostatic method in which the pointed end of the electrode array 42, 52 project out of the end face of the head substrates 41, 51, or meet the end face thereof. Accordingly, the electrode array would be easy to damage because the recording paper comes into contact with the electrode array. Further, from the view point of the manufacturing method thereof, it can not use a high precision manufacturing technology used in semiconductor manufacturing process such as the stepper exposure technology, thereby there are problems of processing precision, uniformity, and yield and so forth. Particularly, it can not prepare radius of curvature for the pointed end of the head with moderately small and uniformly, consequently it is necessary to apply high voltage to the pointed end of the head, with the result that it would be disturbed an implementation for low voltage drive, and there is a problem of an extra ordinary discharge caused by the shape non-uniformity.
When it intends to constitute a multi-head such as a line-head with a plurality of heads, as shown in FIGS. 1 and 2, since the electrode array portion is formed on the surface of the head substrate, the electric field influences between adjacent electrodes with each other with the result that concentration and the jet of the ink-drops from the individual electrode become unstable. As the extensive case, there is a serious problem that the ink-drops repelled by the adjacent electrodes jet between the electrodes.
Further, it is necessary to be formed stably an ink layer at the pointed end of the head by capillary phenomenon in order to jet with the ink condensed and concentrated at the pointed end of the head. However, it is difficult to form stably an ink layer for the reason why the effect of gravity is not equivalent at the pointed end of the head which is formed at the above described end face of the head substrate.
As described above, since the ink-jet printer head in which the color component within the liquid ink is jetted by the conventional electrostatic force, includes the electrode array located at the end face of the head substrate, the recording paper or the like which comes into contact with the electrode array in the printer assembly, which is easy to damage. Further, in regard to the manufacturing of the head, there are problems of the processing precision, the uniformity, and the yield because it can not use the high precision manufacturing technology which is implemented in the semiconductor manufacturing process. Particularly, since it can not be made radius of curvature for the pointed end of the head with moderately small and uniformly, applying high voltage to the pointed end of the head is required, with the result that it would be disturbed an implementation for low voltage drive, and there is a problem of an extra ordinary discharge caused by the shape non-uniformity. When it intends to constitute a multi-head, since the electrode array portion is formed on the surface of the head substrate, the electric field influences between adjacent electrodes with each other with the result that concentration and the jet of the ink-drops from the individual electrode become unstable. As the extensive case, there is a serious problem that the ink-drops repelled by the adjacent electrodes jet between the electrodes. Further, it is necessary to be formed stably an ink layer at the pointed end of the head by capillary phenomenon in order to jet with the ink condensed and concentrated at the pointed end of the head. However, there is a problem that it is difficult to form stably an ink layer for the reason why the effect of gravity is not equivalent at the pointed end of the head which is formed at the end face of the head substrate.